NASA researchers have been interested in the effects of space travel and in particular microgravity (μg; not to be confused in this context with the common abbreviation for micrograms) on stem cells. For instance, see the past piece“Stem Cells Take Wild Ride in Space Capsule”.

In a new NASA study led by Dr. Eduardo A.C. Almeida, the researchers found that μg reduced the regenerative capacity of mouse embryonic stem cells (mESC).

The mESC taken to space exhibited altered behavior including reduced differentiation into a variety of specialized cell types (see Figure 5 from the paper that summarizes the changes).

Normally mESC are pluripotent, meaning that they can be stimulated to form any murine cell type. The mESC that travelled into space, in contrast, did not differentiate normally and failed to turn on specific differentiation markers. Instead they were shifted more toward an undifferentiated phenotype even when signaled to differentiate.

“In this study, we found that spaceflight in μg promoted the maintenance of EB stem cell gene expression and post-μg reloading differentiation potential, defined as “stemness”, and inhibited the appearance of differentiation markers for multiple tissue lineages. These findings may have important implications for the maintenance of tissue regenerative health in both astronauts during short and long-duration spaceflight in μg conditions, and for humans on earth.”

The μg mESC were, however, able to form embryoid bodies (EBs), the early stage of mESC differentiation, apparently normally and did not exhibit reduced survival during differentiation.

There may be subtle differences in other aspects of cell biology of μg mESC such as cell cycling, cell metabolism and signaling. For these studies, the μg mESC were compared to so-called “ground control” mESC.

These studies suggest that astronauts in space for extended periods of time may exhibit health changes associated with alterations in their stem cell biology. It will be interesting to see follow up work including in particular on human embryonic stem cells (hESC) and induced pluripotent stem cells (IPSC), which seem like logical next steps.